The major objectives of this research are to: (1) Determine the prevalence of social, emotional and cognitive and/or other developmental dysfunctioning among preschool children; (2) To investigate the relationship of these areas to later school functioning and emotional problems; and (3) In order to do this, to develop, refine, and validate a screening battery that can be utilized in locally and nationally mandated screening programs. From 1976 to 1979, approximately 4,400 children in three cohorts will be screened for the above "risk" factors. Intensive studies will be made of samples of children determined "at risk", and an equal number of not "at risk" children to be followed for the duration of the project. Analysis will describe the prevalence of dysfunctioning as well as the relationship of variables identified at screening to later problems. An ultimate aim is to create an economical and efficient procedure that can aid in early identification of mental health problems and result in appropriate and timely intervention.